Telephone system



G. A. YANOCHOWSKI.

TELEPHONE SYSTEM.

APPLICAIION FILED AUG.22. 1910.

I 1,405,175. Patented Jan. 31, 1922.

2 SHEETS-SHEET l.

G. A. YANOCHOWSKI.

TELEPHONE SYSTEM- APPLICATION FILED AUG.22. 1919.

Patented Jan. 31, 1922.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

GEORGE A. YANOGHOWSKI, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCH- IBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLI- NOIS.

To all whom it may concern:

Be it known that I, GEORGE A. YANO- OHOWSKI, a citizen of the United States of America, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to telephone systems and has to do more particularly with systems of the type in which automatic switches are employed at the exchange or central office for establishing connections between subscribers lines.

A general object of my invention is the provision of improved circuit arrangements for the automatic switches.

One of the features of my invention is the provision of a frequency selector associated with a connector switch, provided with differential switching relays, which is actuated by series of impulses to select the proper ringing current generator to actuate the call bell of the desired substation.

A further feature of my invention is the provision of a frequency selector of the type above described, which is provided with holding means that is released by the connector switch when it is released.

A still further feature of my invention is the provision of a system of the character above described in which, when the called subscriber responds, the ringing current is instantly disconnected, no matter whether the called subscriber responds during a ringing interval or a silent interval.

A still further feature of my invention is the provision of a system of the above character for operation with connectors of the side switchless type and of the step-ahead release type.

The above and other features of my invention will be hereinafter more fully described in the ensuing specification and more particularly pointed out in the appended claims.

For a better understanding of my invention reference may be had to the accompanying drawings which comprise Parts 1 and 2. In order to more fully understand the circuits as pointed out, Part 2 is placed to the right of Part 1 to form a continuation thereof and to-form a complete circuit arrangement between'a calling-and a called substation.

Specification of Letters Patent. Patented Jan, Application file d August 22, 1919. Serial No. 319,050. j

Referring now more particularly to the system as shown in Part 1, the substation A comprises the usual switch-hook and substat on equipment, and includes a calling device CD. -The said substation A is connected, by means of the two line limbs as shown, to a line switch B at the exchange. The said line switch B is adapted, upon the initlation of a call from substation A, to automatlcally connect with an idle first selector C. The subscriber at A, by the use of the calling device CD in connection with his substation equipment, operates the firstselector C to extend the connection from the substation A to an idle connector switch D. The subscriber at A then, b further actuations of his calling device D, operates the connector switch D to extend the connection to the terminals of the called-for line E. To the right of the drawing in Part 2, I illustrate a frequency selector FS and. by the use of the calling device CD the subscriber at substation A may actuate the frequency selector FS to select the proper generator frequency to ring the call bell of a called-for substation. If the called line is idle, ringing current is automatically applied to the terminals thereof to signal the called-for subscriber. Should the line of the called-for subscriber be busy, a characteristic busy signal will be automatically transmitted back to the calling subscriber who may, by replacing his receiver upon the switch-hook, release the switches which were used in extending the connection to the called-for subscriber. The line switch B may structurally be of the type shown in co-pending application, Serial Number 271,960, filed by H. H; Ide, January 20, 1919.

The switch B, as diagrammatically illustrated, comprises a double-wound line and test relay LR, a single-wound cut-0E relay CO, and a motor magnet MM. The line relay LR is adapted to be energized over the two sides of the subscribers line in series; the cut-off relay CO is adapted when energized to disconnect the subscribers line circuit from the line relay LR, and to connect the switch wipers to the subscribers line when the line switch B is used for calling purposes. A motor magnet MM is provided for stepping the switch shaft and wipers 2, 3 and 4 step. by stepover the bank contacts 5, 6v

and 7. The switch wipers 2, 3 and 4 are adapted to be rotated always in the same direction and do not restore to normal, that is, the switch wipers do not have a normal contacts ON are so arranged that when the line relay LR is energized, they are moved to their off-normal position and are returne to their normal posltion by the energization of the cut-off relay'CO, that is, these olfnormal springs are so arranged that when the line relay LR is energized a catch mechanism is operated to release the off-normal springs to their operated position, and upon the energization of the cut-off relay CO the springs are returned to their normal positlon, in which osition the catch mechanism again is brought into operation to hold the off-normal springs in their normal position. Reference may be had to said Ide application S. N. 271,960 for a more complete understanding of the mechanical construction of the line switches B and B.

The switch shaft which carries wipers 2, 3 and 4; is provided with a ratchet mechanism which is adapted to co-operate with the driving pawl controlled by'the motor magnet MlW to rotate the switch shaft and wipers in a clockwise direction.

A further mechanical arrangement is pro, vided for the line switch and connects the line relay LR and the cut-off relay CO in such a manner that the armature of the cutoff relay CO can not be fully attracted unless the line relay LR has been energized first, that is, if the line relay LR has been energized, the armature of-the cut-ofi' relay CO may then be energized to move its switch contacts to their alternate positions, while if the cut-off relay CO is energized before the line relay LR is operated, the armature of the cut-off relay CO is permitted to move only far enough so that its contacts 9, 10 and 11 move from engagement with their back contacts 12, 13 and-'14, respectively, but not into engagement with their front contacts 15, 16 and 17. This feature is provided so that-when the substationA is called from a connector switch and the cut-off relay CO energized, the subscribers line can bedisconnected from the line relay LR of the switch B, but cannot be connected with the switch wipers of the switch.

The circuits shown for the selector switch vC and connector switch D are adapted to relay IR, which relay is energized and deenergized by impulses from the calling device CD at the calling substation A, and the eneifiitzation and de-energization of the relay brings about the actuation of the primary ma et PM to step the first selector switch wlpers 18, 19 and 20 in a primary direction to a certain oulp of contacts. secondary magnet S is provided for said selector which automatically steps the wipers 18, 19 and 20 in a secondary direction over the contacts 21, 22 and 23 in the selected group in search of a set of contacts leading to an idle connector D. A switching relay T is also provided, which when energized extends the connection of the calling substation A to the idle connector D. Primary and secondary off-normal contacts PON and SON, respectively, are provided. The said primary off-normal contacts PON assume their alternate position on the first step of the wipers 18, 19 and 20 in a primary direction, and the secondary off-normal contacts SON assume their alternate position upon the first step of the wipers 18, 19 and 20 in a secondary direction over contacts 21, 22 and 25.

The connector switch D is provided with an impulse relay IR, responsive to the impulses of the calling device CD at the calling substation A, which relay IR brings about the actuation of the primary magnet PM to step the connector switch wipers 24, 25 and 26 in a primary direction to a certain group of contacts containing contacts of the called line E. A switching relay SW is provided which is energized upon the'termination of the first set of impulses to connect the secondary magnet SM in circuit with the impulse relay IR, to be actuated by the energization and the de-energization thereof to step the connector switch wipers 24, 25 and 26 over the contacts27, 28 and 29 in the selected group to the contacts of the called line. A switching relay SW is also provided which is energized after the termination of the last set of impulses which step the wipers 241, 25 and 26 into engagement with the contacts 27, 28 and 29 of the called substation E. The relay SW upon energization places the motor magnet MM of the frequency switch FS in association with the impulse relay IR so that the impulses transmitted from the calling device CD at calling substation A actuate the frequency selector switch to select the proper frequency of ringing current to actuate the call bell at the called substation E. A shaft 32 is provided for the switch F S, which carries the wiper vided for the motor magnet MM, and operates to step the wiper 30 from one contact to the next to select the proper frequency generator G, G, etc., to signal the called.

substation E. A retaining pawl 35 is provided which engages the ratchet 33 and holds the wiper 30 in its advanced position, to which position it has been stepped; The retaining pawl 35 is operatively associated with the shaft of the connector switch D and after the termination of conversation the connector restores to normal and its shaft engages the retaining pawl 35, withdrawing it from engagement with ratchet 33, allowing the wiper 3.0 to restore to its normal position under spring tension. In the drawing I show, for the sake of clearness, only generators G and G connected through interrupters I and I -to supply interrupter generator ringing current. However, there will be as many generators and interrupters as there are substations on the called line to signal. Of course, other than the harmonic system of signaling may be used, for example, pulsating current may be used and the substations connected from each side of the line to ground, etc.

A test control relay TCR is provided which is used to test the called lineas to its idle or busy condition, and a test relay TR is provided which is actuated upon connection with a busy called line through the agency of the relay TCR. The relay TR operates when engaging a busy line to connect busy-back apparatus BB to the calling substation to notify the calling subscriber of the busy condition of the called line and disconnects the relay TCR from the test wiper 24. A ringing trip relay RT is also shown which is operated when a called subscriber removes his receiver in repsponse to a call, the said relay RT opening the ringing circuit to disconnect the ringing current from the called line. Should a called subscriber remove his receiver during either a ringing or a silent period, the ringing current is immediately disconnected, as will be more fully hereinafter described. The relay RT is provided with a locking winding to prevent a reapplication of rin ing current to the called subscribers line prlor to a disconnection of the connector D from the line of the called subscriber. With this ringing arrangement, it is only necessary to provide one control relay for theringing current. A back bridge or supervisory relay SR is also provided, which operates upon the actuation of the ringing trip relay RT. Primary and secondary off-normal contacts PON and SON are provided and assume their alternate positions, respectively, upon the primary and secondary movements of the wipers 24, 25 and 26.

To the right of the drawmg in Part 2, I

show a called substation E, similar to that of A, the said subscriber being provided with a line switch B, similar to line switch B.

Having described in general the structure of the switches and apparatus, 1' will now explain more in detail the operation of the same.

Assuming that a call is to be traced from the calling substation A to the called substation E, upon the removal of the receiver by the subscriber at the calling substation A, line relay LR of switch B is energized by current traced from battery, through the upper windin of relay LR, contact 40 of motor magnet M, normal contact 41 of offnormal s rings ON, contacts 14 and 11 of relay C6 through the calling substation back through contacts 9 and 12 of relay CO and through the lower winding of relay LR to ground. Line relay LR upon energizing trips the off-normal contacts ON to their operated position. As before mentioned, wipers 2, 3 and 4 always rest upon the set of contacts 5, 6 and 7 last used, and assuming the contacts upon which the Wipers now rest are busy, due to another subscribers line switch having selected the first selector last used'by the subscriber A, the engaged private contact 5 will be found to contain a busy potential. The tripping of off-normal contacts ON connects the upper winding of line relay LR tothe private bank contact 5, which we have assumed contains a busy potential, over a circuit extending from battery, through the upper winding of relay LR, normal contact 40 of motor magnet MM, alternate contact 41 of off-normal springs ON, contacts 13 and 10 of relay CO, to private wiper 2 and-the grounded bank contact 5.- The line relay will thus remain energized until its circuit is opened at contact 40 of the motor magnet MM. The closure of contact 42 of relay LR closes a circuit for motor magnet MM, extending from battery, through the winding of said motor magnet MM, contact 42 of relay LR, to the private wiper 2 and grounded busy bank contact 5. v

The motor magnet MM upon energizing opens the circuit of test relay LR at its contact- 40, thereby permitting the same to deenergize. The motor magnet at the same time, of course, steps the wipers 2, 3 and 4 to the next set of bank contacts. The line and test relay LR restoring opens its contact 42, thereby opening the circuit of motor magnet MM and permitting the said motor magnet MM to restore. Should the contacts now engaged by the wipers be busy, relay LR again energizes by current through normal contact 40 of motor magnet MM and again closes contact 42, energizing motor magnet MM, as before described. The line and test relay LR and magnet MM are thus set of contacts to the next as long as busy, that is, as long as grounded contacts 5 are encountered, and relay LR energizing each time a grounded bank contact is encountered. Magnet MM alternately opens and closes its contact 43, and thus a vibratory circuit is closed through the winding of cutoff relay CO to ground, through contacts 44 of off-normal contacts ON. The Winding of relay CO is of high resistance and as motor magnet MM is energized and de-energized with great rapidity, the said winding of relay CO does not effectively energize and attract its armature while the motor magnet MM is operating. The relay OO may also contain a copper sleeve to make it slightly slow to energize. Closure of contacts 44 of off-normal contacts ON places a ground upon private normal contacts 45 at the connectors having access to the calling subscribers line A to render such contacts busy to incoming calls. When an idle rivate contact 5 is encountered, test relay L and magnet MM remain unoperated and the prolonged closure of contact 43 of magnet MM now effectively energizes the relay CO by current over a path traced from battery, through the winding of relay CO, contact 43 of motor magnet MM, and contact 44 of off-normal contacts ON to ground. Relay CO upon energizing restores the off-normal contacts ON to their normal positions, connects the subscribers line to line wipers 3 and 4 and connects the said winding of relay CO to private wiper 2. The relay CO being slow to release is held up momentarily until a substitute circuit is established for the relay CO, as will be presently described.

The connection of the subscribers line to line wipers 3 and 4 of the switch B closes an energizing circuit for impulse relay IR of the idle first selector C over a circuit traced from battery through the right-hand wind ing of relay lR conductor 46, contact 47 of relay T, contact 6, wiper 3, alternate contacts 15 and 9 of relay CO, through substation A, back through alternate contacts 11 and 17 of relay CO, wiper 4, contact 7, normal contact 48 of relay T, conductor 49 and through the left-hand winding of relay IR to ground. The closing of alternate contact 50 of relay IR energizes relay 51 by current from battery, through the upper winding of relay 51, contact 50, to ground at normal contact 52 of the primary off-normal contacts PON. Relay 53 is also energized, due to the closure of alternate contact 50 over a circuit traced from battery, through the upper winding of said relay 53, and alternate contact 50, to ground at normal contact 52 of primary 011:- normal contacts PON. The closing of alternate contact 54 of relay 53 establishes a substitute energizing circuit for relay C0 of the line switch C before it has had time to deenergize, said circuit being traced from battery, through relay CO, normal contact 43, contacts 16 and 10 of relay CO, wiper 2, contact 5, conductor 55 and alternate contact 56, to ground at alternate contact 54. Relay CO remains energized until time of release. The connector contacts 45 of substation A are also made busy by the ground just traced.

1f the private contact 5 engaged by the wiper 2 is idle when the subscriber A initiates a call, the line relay LR is energized as before described, and contacts ON assume their alternate position, but the closing of contact 42 of relay LR does not energize magnet MM since there is no ground on contact 5 and the ma net MM remains inert. The cut-ofl relay CO is immediately energized to ground at contact 44, restores contact ON as before described, and the relay CO is held energized over a circuit to ground at first selector O, as already described. Thus switch B only travels when its wipers are in engagement with a busy trunk when a call is lnitiated.

An idle first selector C. having been seized as just described, and assuming that the number of the called substation E is 345 the subscriber A actuates the calling device CD to send three impulses of current over the line, which impulses bring about three rapid de energizations and energizations of the impulse relay IR. The primary magnet PM is energized and de-energized three times, due to the closing and opening of normal contact 50 of relay IR, the circuit being traced from battery, through magnet PM, normal contact 57 of secondary offnormal contact SON, conductor 58, normal contact 50 of .relay IR, conductor 20 to ground at alternate contact of relay 51, which magnet operates to step the wipers 18, 19 and 20 of the first selector O in a downward primary direction to the third group of contacts, thus selecting the threehundreds group of connectors. After. the last impulse, the relay 53 de-energizes, due to a circuit being closed through the lower winding of the said relay 53, normal contact 59 of magnet SM, alternate contact 60 of relay IR, and alternate contact 61 of primary off-normal contactsPON to ground at alternate contact 52 of primary 0'snormal contacts PON. The primary 011"- normal contacts PON move to their alternate positions upon the first step of the wipers 18, 19 and 20 of the first selector D ofi-normal', and the energizing circuit for the lower winding of relay 53, just mentioned, is closed uponv the first step of the wipers of? normal, but the relay 53 does not de-energize during the sending of impulses,

it being diiferentially wound and only rethe rapid operation of relay IR, althoughrapid impulses are transmitted through 1ts lower or neutralizing winding, due to the construction and adjustment of the said relay 51. Upon the de-energization of the relay 53, an energizing circuit for the relay 62 is established, traced from battery, through the winding of said relay, normal contact 63 of relay T normal contact 64, normal contact 65 of the secondary offnormal contact SON, normal contact 54 of relay 53 and alternate contact 56 to ground .at alternate contact 52 of primary off-normal-'contactsPON. Relay 62 causes secondary magnet SM to be energized over a circuit traced from battery through said mag-' net SM to ground atalternate contact 66 of relay 62, and secondary magnet SM steps the wipers 18, 19 and 20 one step in a rotary or secondary direction into engagement with the first set of contacts 21, 22 and 23, and the opening of normal contact 64 at magnet SM de-energizesrelay- 62. The opening of normal contact 59 of magnet SM opens the circuit through the lower winding of relay 53, which relay energizes again. Relay 62 upon de-energization opens its contact 66,

permitting secondary magnet SM to deenergize. Upon the first step of the wipers 18, 19 and 20, the secondary off-normal contacts SON assume their alternate position, opening the initial energizing circuit of the relay 62, and should the private wiper 18 r of the first selector-D engage a contact leading to a busy connector, a substitute circuit is established for relay 62 traced from battery, through the winding of the relay 62, normal contact 63 of relay T, normal contact 64 of magnet SM, alternate contact 67 of relay 51, alternate contact 28 and wiper 18 to the grounded busy contact 21. The resulting closing of contact 66 of relay 62 again energizes secondary magnet SM. The relay 62 and magnet SM are thus alternately energized'and de-energized to step the wipers 18, 19 and 20 in a secondary rotary directionto seek the contacts of an idle connector switch as D. When a contact 21 leadingto an idle connector is encountered by the wiper 18, the energizing circuit for relay 62 remains open and no further energizations of the secondary magnet SM occur. By this see-saw action of relay 62 and magnet SM a positive driving operation of the secondary magnet SM is secured and the selector C will not stop on a busy contact or go past an idle contact, because unless relay 62 is energizedfmagnet SM can not be energized, and relay 62 can only be energized when magnet SM is at normal and private wiper 18 is resting on -a busy contact.

The relay 53 does not de-energize during the secondary movement of the wipers, due to its adjustment and the rapidity of the interruptlons of contact'59 of secondary magnet .SM. The steady closure of contact 59 of magnet SM after its last de-energization closes a circuit for the lower winding of the relay 53, as previously described, and due to its diflerential construction, it de-enernormal contacts 47 and 48 of relay T opens the energizing circuit. of the impulse relay IR, and the closing of normal contact 50 of said relay IR closes a circuit through the lower winding of the relay 51, traced from battery, through the said lower Winding, contact 56', and normal contact 50 of relay IR to ground at contact 70 of relay 51, which relay 51,-due to its differential winding neutralizes and restores to normal, and opens, the circuit of relay 53 permitting the latter to restore. The closing of alternate contacts'47 and 48 of relay T extends the connection of the calling subscriber A to the idle connector D, engaged by Wipers 4 1'8, 19 and 20 of the first selector, bringing about the energization of the impulse relay. IR of connector D over a circuit traced from ground through the right-hand winding of the relay IR, contact 23, Wiper 20, alternate contact 48 of relay T, contact 7, wiper I for it, traced from battery through the winding of said relay, its alternate contact 71, wiper 18, bank contact 21, conductor 72, and conductor 73 to ground at alternate contact 74 of the impulse relay IR. The said relay T remains energized until the termination of the conversation.

The energization of the relay IR brings containing the contacts of the called line..

about the energization of the rela s7 5 and 76, the circuit of relay exten ng from battery through the right-hand wind ng of said relay, normal contact-77 of the prlmary off-normal contacts PON, conductor 72 and conductor 73 to ground at alternate contact 74 of relay IR. The circuit for relay 76 extends from battery through the lower Winding of the relay 76, conductor 78, conductor 79 and alternate contact 80 of relay IR to ground at alternate contact 74 of 1mpulse relay IR. Upon the energization of relay 75, a locking circuit. is closed for the said relay 75 extending from batter through its alternate contact 81 to groun A circuit is closed through the upper winding of relay 76 at contact 82 of relay 75 when it energizes. The closing of this circuit causes the relay 76 to be de-energized, due to its differential construction. However, the de-energization of relay 76 is without effect at this time because the instant therelay IR, causing the primary magnet PM to energize and de-energize four times to step the Wipers 24, 25 and 26 in a primary d1rect1on to the fourth group of contacts The circuit of the primary magnet PM may be traced from battery through the winding of the said magnet PM, normal contact 83 of switching relay SW, conductor 84, normal contact 85 of switching relay SW, conductor 86, alternate contact 87 of relay 76, normal contact 80 of relay IR, conductor 73, conductor 72, normal contact 77 of the primary ofi-normal contacts PON to ground at alternate contact81 of relay 7.5. The primary ofi-normal contacts PON assume their alternate positions upon the first step" of the wipers ofl: normal. :The opening of the primary off-normal contact 77 substitutes a ground from contact 88 of relay 89 for the ground fedthroughcontact 81 of relay 75. After the last impulse of the series has been sent, the steady flow of current through both windings of relay 76.

causes the said relay 76, due to its difierential action, to neutralize and restore its contacts to normal. Relay 76 does not restore during the sending of impulses, due to its ad ustment, construction and the rapidity of the interruptions of contact 80. I

The closing of normalcontact 90 of relay.

76 brings about the energization of the switchingrelay- SW, traced from battery through the winding of said relay SW, its

make-before break contact 91, normal con tact 92 of secondary off-normal contacts SON, conductor 93, normal contact 90 of relay 76, and conductor 94 to ground at alternate contact 95 of primary oif-normal relay SW closes a locking circuit for itself I traced from battery, through-the winding of relay SW, alternate contact 96, conductor 97, normal contact 98 of relay TOR, con- Y ductor 94 to round at alternate contact 95 of primary o-normal contacts P'O'N. The said'relay SW remains energized until the relay TCR is actuated, as will be presently described. The closing of alternate contact 83 of switching relay SW now renders the secondary magnet SM operative so that when the calling subscriber at the substation A actuates his calling device again to send the next set-of impulses, which we have assumed are five in number, the said ma SM will be energized and de-energizetI the impulse relay IR five times over a circuit traced from battery through the wind ing of the said ma et S alternate contact 83 of relay S contact 85 of relay SW, conductor 86, alternate contact 87 of relay 7 6, normal conconductor 84, normalnet tact 80 of relay-IR, conductor 73, conductor 72, alternate contact 77 of the primary offnormal contacts. PO'N, and conductor 100 to ground at normal contact 88 of relay 89. The secondary magnet SM now steps the wipers 24, 25 and 26 .in a secondary direction to engagecontacts 27, 28 and 29 of the called line. Upon the first impulse of this set, that is, upon the o ening of contact 80 of relay IR the relay 7 6 again energizes to permit the secondary magnet SM to be operated, and after the last impulse the relay 76 is again de-energized by having a circuit closed through its lower winding, as-p-re viously described. The. restoration of the relay 76 closes a circuit for the switching relay SW,.traced from battery through the Winding of the said relay SVVL', conductor 101, its normal contact 102, conductor 103, alternate contact 104 ofrelay SW, conductor 105, alternate contact 92 of secondary ofl normal contacts SON, conductor 93,

normal contact 90 of relay 76,.conductor 94 to ground at alternate contact 9501? primary off-normal contacts .PO'N.- The closing of alternate contact. 106 of relay SW establishes a locking circuit for the said relay SW traced from battery through the winding of relay S-W, alternate contact 106, conduetors 107 and 94 toground at alternate contact 95 of primary oif-normal contacts PON', the said relay SVV' remaining energizcd until the restoration of the switch D.-

The subscriber at the calling substation A now act-uates hiscalling device CD to send impulses of current to bring about the movement of the frequency switch wiper 30 over contacts 31 to select the proper generator frequency to actuate the call bell at the called substation E. Assuming that the desired party is the first party or subscriber E on the party line, the subscriber at the calling substation A now actuates the calling device CD thereat to transmit one impulse of current, which brings about one de-energization and energization of impulse relay IR. The de-energization of relay IR, due to the impulse of current, allOWS relay 76 to again energize, as previously described, and closes a circuit for the motor magnet MM of the frequency switch FS over a circuit traced from battery, through the winding of the magnet MM conductor 108, alternate contact 85 of switching relay SW, conductor 86, alternate contact 87 of relay 76, normal contact 80, conductors 73 and 72, alternate contact 77 of primary oil-normal contacts PON, conductor 100 to ground at normal contact 88 of relay 89. The magnet MM upon energization causes pawl 33 to engage a tooth of ratchet 34, rotating the wiper 30 one step into engagement with the first contact 31, which contact is connected through interrupter I to generator G,which we assumed is the proper generator frequency for actuating the call signal at the called substation E. The retaining pawl 35 engages a tooth of the ratchet 34 and holds the wiper 30 in engagement with the contact 31 until restored, as will presently be vdescribed. The impulse relay IR again energizes after the impulse has been transmitted and again closes a circuit through the lower winding of relay 76 as previously described, allowing the relay 76 to restore, due to its differential construction, and also preventing further actuation of. magnet M-M'. The restoration of relay 76 closes a circuit for the test control relay TOR, traced from battery. through the winding of relay TOR, conductor 110, closed contacts 111 and 112, which contacts are controlled by the shaft 32 of the frequency switch F'S and assume their alternate position on the first step of the wiper 30 off normal, conductor 113, alternate contact 114, conductor 103, alternate contact 104 of relay SW, conductor 105, alternate contact 92 of secondary off-normal contacts SON. conductor 93. normal contact 90 of relay 76, conductor 94 to ground at alternate contact 95 of primary ofi' normal contacts PON'.

The relay TOR upon energization opens the locking circuit of switching relay SW at its contact 98, permitting the said relay SW of alternate contact 1150f relay TOR connects the test relay TR in multiple circuit with relay TOR to the, test wiper 24, the circuit of the test relay'TR being traced from batte through the winding of the said relay T its Inake-before-break contacts .116. conductor 117, normal contact 104, conduc tor 103, alternate contact 114 of relay SW, conductor 113, closed contacts 111 and 112, conductor 110, alternate contact115, conductor 120, normal contact 121 of relay TR, conductor 122 to wiper 24. The: circuit of relay TOR. may be traced from battery, through the winding of relay TOR, its'alternate contact 115, conductor 120, normal contact 121 of relay TR and conductor 122 to the test wiper 24.

Owlled me idle.

Assuming that the called line is idle, private contact 27 of the called line will have a battery potential upon it and the relay TR will not be energized, but will remain at normal and the relay TOR failing to find a ground upon wiper 24 returns to normal, having its initial energizing circuit opened at alternate contact 104 of relay SW, as be-'- fore described.

The relay TOR de-energizing brings about the energization of the relay 89 over a circuit traced from battery through the cutofi' relay O0 of the individual line switch B, bank contact27, through wiper 24, conductor 122, normal contact 121 of relay TR, conductor 120, normal contact 115 of relay TOR, conductor 123, normal contact 124 of relay SW, conductor 125, through the lower winding of the relay 89, conductor 126, to

round at alternate contact 82 of the relay 5. Relays 89 and O0 energize over this circuit. Relay OO' upon energizing, removes the called subscribers control of the line switch B.

The closing of alternate contact 127 of relay 89 short-circuits the lower winding of the said relay and feeds ground to the cutoff relay C0 of the line switch B, and at the same time supplies the busy potential to the multiple private contacts 27 of the called line. The closing of alternate contact 128 of relay 89 closesa circuit through' the upper winding of said relay 89, traced from battery through its winding, the alternate contact-128 of said relay 89, and conductor 126 to ground at alternate contact 82 of relay 75. The closing of alternate contact 129 of the relay 89 closes a circuit for ringing current from generator Or to signal the called subscribers substation, the path of said ringing current being traced from battery 130,

thnough; the ringin generator G, through the live segment the interrupter I, ooh- I tact 31 and wiper 30 of the freguency switch FS, through the winding 132 0 relay TR, conductor 133, alternate contact 129 of relay 89, conductor 134, normal contact 135 of relay RT, wiper 26, contact 29, through the call bell and condenser of the called substation E, back through contact 28, wiper 25, normal contact 136 of relay I RT and conductor 137 to ground at alternate contact'88 of relay 89. The ringing current is intermittently connected to the called line,

due to the constantly rotating interrupter I, thus bringing about an intermittent actuation of the call signal at the called subscribers substation E. The'interrupter I is so arranged that ringing current from the generator G and battery 130 are alternately connected to the called line, so that should i the subscriber answer. in either a silent or a' ringing period, ringing current is instantly disconnected, thus eliminating the undesir-' able feature of ringing-the answering subscriber at the called.- substation in the ear should the subscriber remove his receiver duringa ringing period. During the ringing and silent periods, and before the sub 132 of the relax scriber at the called substation E answers, the condenser at the said' substation prevents a How of battery through the winding RT. The calling subscriber at substation also receives an audible signal notifying him that the called subscriber is beingsignaled; the audible signal circuit being traced from the ungrounded pole of the generator G through resistance 140,

condenser 141, normal contact 142, conductor- 143, alternate contact 144 of relay 89, contact 23, wiper 20, altermate contact 48 of relay T, contact 7, wiper 4, closed. contacts 17 and 11 of relay CO, through the receiver of the calling substation A,-back through closed contacts 9 and 15 of relay CO, wiper 3, contact 6, alternate contact 47 of relay T,

wiper 19, contact 22, to groundthrough the upper winding of supervisony relay S The subscriber in response to the call signal, removes his receiver, and should he remove it' during a live period the combined generator and; battery current of the generator G and battery 130 brings about the energization of the rela RT over a circuit traced from battery 130, t rough the said generator G, through the interrupter I, the upper winding 132 of relay RT, conductor 133, alternate contact-129, conductor 134, normal contact 135','wiper 26 and contact 29, through ringing trip segments of the interrupter I, the .upper winding 132 of relay RT, and over the previously described path to ground at alternate contact 88, which causes the relay RT to en ergize and close the locking circuit for itself t rough its winding 138-, as before described. T s it will be seen that ringing current is instantly disconnected from the called line either during live or silent periods by the opening of contacts'135 and 136 of relay RT. Uponthe energization of the relay RT, an ener 'zing circuit for the supervisory re lay R' is established traced from battery through the lower winding of said relay SR, alternate contact 135 of relay RT, wiper26, contact 29,-through the substation back to the contact 28, wiper25, alternate contact 136 of relay RT and through the. upper winding of the relay SR to ground. The subscribers are now in conversational circuit and the talking circuit may be traced over the heavily marked conductors, the said conductors having the condensers K and K interposed.

The subscribers having finished conversation, and assuming that the subscriber at the substation A is the first to replace his receiver upon its switch hook, the opening of the switch hook contacts thereat brings about the de-energization of the impulse relayIR of the connector D. The restoration of the relay IR brings about the opening of the holding circuit of the relay T of the first selector 0, and the closing of normal contact 63 of the restored relay T of the first selector C' closes an energizing circuit for the relay 62, which may be traced from battery through the winding of the relay 62, normal contact 63, normal contact 64 of magnet SM, normal contact 67 of relay 51, and alternate contacts 61 and 52 of primary off-normal contacts PON to ground. The closing of alternate contact 66 of the relay 62 brings.

about the energization of the secondary magnet SM. The relay 62 and the secondary -magnet SM are alternately energized and deenergized, as previously described the secondary magnet SM thus stepping the wipers 18, 19 and 20 beyond the last contacts of the row of bank contacts, from which point the wipers are restored to normal. The seconda off-normal contacts SON and primary 0 -normal contacts PON restore to normal, and the opening of alternate contact 52 of the primary off-normal contactsPON opens the energizing circuit of the cut-off relay C0 of the individual line switch B. Therestoration of the cut-ofi relay CO restores the indi-, vidual switch B to normal.

The subscriber E placing his receiver upon the switch hook interrupts the circuit of the relay SR of the connector D at the switch hook contacts, causing the said relay to deenergize. The closing of normal contact 15 of relay SR closes a circuit through the lefthand windin of the relay 75, which may be traced from battery through the said lefthand winding of relay 75, through its alternate contact 151, conductor 152, normal contact 150, and conductor 153 to ground at normal contact 74 of the relay IR. Due to the differential construction of relay 75, the said relay neutralizes and restores to normal. The closing of normal contact 154 of relay 7 5 closes the circuit of secondary magnet SM, which may be traced from battery throu h the winding of said secondary magnet SEI', conductor 155, normal contact 154 of relay 75, alternate contact 156 of primary off-normal contacts PO'N', through the interrupter I to ground. The secondary magnet SM thus steps the wipers 24, 25 and 26 beyond the last setoi' contacts in the group, and the wipers then restore to normal from this position. The restoration of the relay 7 5 also brings about the opening of the circuit of the relay 89 at alternate contact 82, bringing about the restoration of the said relay 89. The primary oft-normal contacts PON having restored upon the restoration of the switch, the opening of alternate contact 95 of the contacts PON brings about the restoration of the relay RT and relay SIV.

The relay 75 also causes the de-energization of cut-off relay C0 of the line circuit B, which is associated with the called subscribers substation E. The switch shaft of the connector D upon restoring to normal engages the retaining pawl 35 of the frequency switch FS and withdraws it from engagement with the ratchet 3 1, thus allowing the wiper 30 to restore to normal again, opening contacts 111 and 112. All of the apparatus used in establishing the connection between the calling subscriber at the substation A and the called subscriber at the called substation E is now at normal and available for use in establishing other connections.

Assuming now that the subscriber at the called substation E is the first to replace his receiver upon the switch hook, the opening of the switch hook contacts at the substa-.

tion E brings about the de-energization of the relay SR. Nothing else happens at this time as the relay IR is still maintained energized over the line of the calling substation A. The calling subscriber at the substation A replacing his receiver interrupts the circuit of the impulse relay IR at the switch hook contacts. The relay IR de-energizing, closes acircuit through the left-hand winding of relay 75, causing the said relay to de-energize, as hereinbefore described. The restoration of the individual Should the called subscriber E fail to replace his receiver upon the switch hook after the conversation is terminated, the replacing of the receiver at the substation A brings about the de-energization of the impulse relay IR of connector D, the same as before, and the opening of alternate contact 74 of the impulse relay IR opens the' circuit of the relay T of the first selector C, as before described, and causes the release of the selector C and individual switch B. The subscriber at the called substation failing to replace his receiver upon the switch hook permlts the continued energization of the relay SR, thus holding contact 150 of said relay in lts alternate position, preventing the differentially wound relay 75 from restoring to normal and closing the energizing circuit for the secondary magnet SM. The relay 76 energizes when the impulse relay IR drops back but is immediately restored to normal, due to the closure of an energizing circuit through the lower winding of the sald relay 7 6,'which may be traced from battery through the lower winding of the relay 76, conductor 78, conductor 79, alternate contact 150, conductor 153, to ground at normal contact 74 of the now restored impulse relay IR. The relay 76 being differentially wound restores to normal, and the closing of normal contact 160 of said relay 76 places a ground upon the private contact of the connector D over a circuit which may be traced from ground to alternate contact 95 of primary off-normal contacts PON', over conductor 94:, through normal contact of relay 7 6, conductor 93, alternate contact 92, normal contact 160 of relay 76, alternate contact 161 of secondary off-normal contacts SON and conductor 72 to the private contact 21. The placing of the busy potential upon the private contact prevents any first selector switch C from engaging the contacts of this busy connector.

Called Zine busy.

Assuming now that the called line is busy, the operation of the circuit is the same up to and including the time when the relay TOR energizes, as previously described. The line being busy, private contact 27 has a busy potential placed upon it, thus closing the multiple circuit for the relay TCR and the test relay TR, the circuit of the relay TOR being traced from battery through the winding of the said relay TCR, its alternate contact 115, conductor 120, normal contact 121 of relay TR, conductor 122, to the busy grounded private contact 27. The circuit of the test relay TR is traced from battery through the winding of the said relay T'R, the make-before-break contact 116 of said 7 primary 0 relay relay, conductor 117 normal contact 104 of relay SW, conductor 103, alternate contact 114 of relay SW, conductor 113, closed contacts 111 and 112, conductor 110, alternate contact 115 of relay TCR, conductor 120, normal contact 121 of relay TR, conductor 122 and wiper 24 to ground at busy private contact 27. The contacts 116 and 121 of the relay TR are so adjusted that the alternate contact 165 makes before the contact 121 breaks, thus closing a locking circuit for relay TR through its alternate contact 165 before the normal contact 121 of the said relay breaks. The lockingcircuit of the said rela TR extends from battery through the said relay, its alternate contact 165, conductor 166, to round at alternate contact 95 of fi-mormal contacts PON. The locking circuit for the said test relay TR is independent of the grounded private contact and'the opening of the normal contact 121 of the relay TR opens the circuit for the TCR which restores to normal. The falling back of relay TCR does not affect relay 89, due to the fact that the test conductor 122 is held open at contact 121 of relay TR. The locking circuit for the test relay TR is thus independent of the busy grounded contact 27 This arrangement does away with the method usually employed of locking the busy relay up to the busy private contact of the called busy line. The closing of alternate contact 167 of relay TR connects the bu'sy-back signal BB to the calling line to transmit a busy signal to the said calling subscriber at the substation A, thus notifying him of the busy condition of the said called substation E.

The calling subscriber now replaces his receiver upon the switch hook, bringing about the de-energization of IR. The relay IR' restoring opens the circuit for the relay T of the first selector C, which closes the circuit. of the secondary magnet SM as previously described, thus bringing about the release of the first selector O and individual switch B. The relay IR de-energizing brings about the restoration of relay 75, due to the fact that the relay SR' is not energized. The closing of normal contact '154 of the said relay closes the circuit for the secondary magnet SM, which magnet steps the wipers 24, 25 and 26 beyond the last set of contacts. The wipers then restore to normal. Primary off-normal contacts PON and secondary off-normal contacts SON are also restored. The apparatus used in this busy connection is now at normal and available for use in establishing other connections. Should the called line become idle during the time of the transmission of the busy signal and before the calling subscriber replaces his receiver, nothing happens as the contact121 of relay TR is in its alternate position, preventing the energization of relay 89, and thus preventing ringing current from being sent out to the now idle called line.

While I have shown a system of 1,000-linc capacity, it is to be understood that by inserting second selectors this system may be increased to 10,000 lines, etc.

'While I have described my invention opcrating in connection with a well-known system, I do not wish to be limited to this exact disclosure, as my invention may be applied to other systems without departing from the spirit of the invention, and I, therefore, do not wish to be limited to this exact disclosure, but aim to cover all such changes and modifications as come within the spirit and scope of the appended claims.

Having described my invention, what I claim as new and desire to secure by United States Letters Patent, is:

l. A telephone system including a called and a calling subscribers line, a side-switchless connector switch, means for connecting said connector switch to said called subscribers line, ringing current generators, a frequency selector for said connector switch, subscriber-controlled means for operating said frequency selector to select one of said ringing current generators, automatic means for intermittently applying ringing current from said selected generator to the called subscribers line, and subscriber-controlled means for disconnecting the selected generator from the called line during a ringing period if the called. subscriber answers during a ringing interval.

2. A telephone system including a called and a calling subscribers line, a side-switchless connector switch, means for connecting said connector switch to said called sub scribcrs line, ringing current generators, a fre uency selector for said connector switch. a difi'erential relay for .placing the control of said frequency selector under the calling subscriber, subscriber-controlled means for operating said frequency selector to select one of said ringing current generators, autotomatic means for intermittently applying ringing current from said selected generator to the called subscribers line, and subscribercontrolled means for disconnecting the selected generator from the called line if the called subscriber answers during a ringing interval.

3. A telephone system including a called and a calling subscribers line, a connector switch, means for connecting said connector switch to said called subscribers line, ringing current generators, a frequency selector Ill - scribers line, subscriber-controlled means for disconnectin the selected generator from the called lme if the called subscriber answers during a ringing interval, holding means for maintaining said frequency selector' in advanced position, and means controlled by the restoration of the connector for actuating said holding means to release the frequency selecton.

4. A telephone system including .a called and a calling subscribersline, a connector switch, means for connecting said connectorswitch to said called subscribers line, ringing current generators, a frequency selector for said connector switch, subscriber-controlled means for operating said frequency selector to select one of said ringing current generators, automatic means'for-intermittently applying ringing current from said selected generator to the called subscribers line, subscriber-controlled means for disconnecting the selected generator from the called line if the called subscriber answers during a ringing interval, and a holding pawl for maintaining said frequency selector inadvanced position, said holding pawl being actuated by said connector when said connector is advanced and restored to its normal position.

5. A telephone system including a calling and a called subscribers line, a side-switchless connector switch adapted to be connected to the calling subscribers line, ringing current generators, a frequency selected for said connector switch, subscriber-controlled means for actuating said connector switch and saidfre uency generator over the two sides of the ca ling subscribers line in series for extending the connection to the calling subscribers line and for selecting one of said ringing current generators, automatic means for intermittently applying ringing currentfrom the selected generator to the called subscribers line, and means responsive to the removal of the receiver at the called substation for instantly disconnecting or for preventing a reapplication of ringing current to the called subscribers line depending upon whether the called subscriber responds during a ringing interval or a silent interval.

6. A telephone system including a called and a calling subscribers line, a connector switch, means for connecting said connector switch to said called subscribers line, ringing current generators, a frequency selector for said connector switch, subscriber-controlled means for operating said frequency selector to select one of said ringing current generators, automatic means for intermittently applying ringing current from said selected generator to the called subscribers line, subscriber-controlled means for disconnecting the selected generator from the called line if the called subscriber answers during a "ringing interval, a holding pawl for maintalning said for said connector switch, subscriber-controlled means for operating said frequency selector to select one. of said ringing current generators, automatic means for intermittently applying ringing current from said selector generator to the called subscribers line, subscriber-controlled means for disconnecting the selected generator from the called line if the called subscriber answers during a ringing interval, holding means for maintaining sald frequency selector in advanced posltion, said holding means being actuated by said connector when it is advanced and restored to its normal position, and differential switching and release relays for said connector switch for controlling circuits thereof.

8. A telephone system 'ncludin a calling and a called subscribers line, a side-switchless connector switch adapted to be connected to the calling subscribers line, ringing curstation for instantly disconnecting or for prc-.-

control. of said relay from a driving magnet of the connector to a driving magnet of the frequency selector.

10. -A telephone system including a connector switch provided with driving magnets, a frequenc 1 Selector for said connector switch provide with a driving magnet, a control relay for controlling said magnets, a circuit, and a differential relay adapted to switch said circuit controlled by said control relay from a driving magnet of the connector to the drivingmagnet of the frequency selector.

11. A telephone system including a connector switch provided with driving magnets, a frequenc selector for said connector switch provide with a driving magnet, a control rela for controlling saidmagnets, an electric conductor, adifferential relay adapted to switch said conductor controlled by said control relay from a driving magnet of the connector to the driving magnet of the frequency selector, holding means for 'maintaining the frequency selector in an advanced position, and means controlled by the release of the connector for releasing said holding means.

12. A telephone system including a connector switch rovided with driving magnets, a frequency se ector for said connector switch provided with a driving magnet, a control relay for controlling said magnets, a circuit controlled by said control re'la a difierential relay adapted to switch sai circuit from a driving magnet of the connector to the driving magnet of the frequency selector, holding means for maintaining the frequency selector in an advanced position, and means actuated when the connector is advanced and restored to release said holding means.

13. A telephone system including a side switchless connector switch provided with a driving magnet, a frequency selector for said connector switch provided with a driving magnet, a control relay adapted to supply impulses of current over a circuit to said driving magnets, and a differential relay for switching the impulse circuit controlled by said control relay from the driving magnet of the connector to the driving magnet of the frequency selector.

14:. A telephone system including a sideswitchless two-wire connector switch, a switch shaft for said connector, a driving magnet for advancing said shaft in one di frequency selector provided with a rection, a second drivin ma et for advanclrection, a freing said shaft in anot er quency selector rovided with a driving magnet, an impu se relay, an im ulse circuit controlled bysaid relay, an a'diiferential relay for switching said impulse circuit from one drivin magnet of the con nector to the other an from said other driving magnet of the connector to the driving magnet of the frequency selector.

15 A telephone system including a side'- switchless two-wire connector switch, 'a"

switch shaft for said connector, a driving magnet for advancin said shaft in one direction, a. second driving magnet for advancing said shaft in another direction, a driving magnet, an impulse relay, an impulsecircuit controlled by said relay, a differential relay for switching said impulse circuit from one driving magnet of the. connector to the other and from said other driving magnet of the connector to the driving magnet of thefrequency selector, and a difl'erential release control relay for controlling the {elease of said connector and frequency seector. I

16. A telephone system'including a sidemagnet for advancing said shaft in one direction, a second driving magnet for advancing said shaft in another direction, a frequency selector provided with a driving magnet, an impulse relay, an impulse circuit controlled by said relay, a differential relay for switching said impulse circuit from one driving magnet of the connector to the other and from-said other driving magnet of the connector to the driving magnet of the frequency selector, a differential release control relay for controlling the release of said connector and frequency selector, means for advancing said switch shaft to restore the same to normal, and means efiectiveupon the restoration of the switch shaft to normal to release said frequency selector.

Signed by me at Chlca in the county of (look and State of Illinois, this 20th day of August, 1919.

GEORGE A. YANOCHOWS'KI. 

